The purpose of this study is to investigate the discriminative stimulus effects of triazolam in combination with several doses of flumazenil. Discriminative responding, self-reports and performance will be assessed under a standard two-response drug discrimination procedure as well as under a novel-response procedure. Under the two-response procedure, the combination of triazolam & a high dose of flumazenil would occasion placebo-appropriate responding while under the novel-response procedure, placebo or novel appropriate responding may occur.